In fixed wing aircraft, the fuel is usually stored in tanks in the main wing. A typical configuration includes a centre tank and a one or multi-compartmented main tank in each wing. In many configurations it is common to have a surge tank located outboard of, and serving, each main wing tank. The main tanks vent through vent lines into the surge tank. Each surge tank vents to atmosphere through an overboard vent which typically includes a NACA intake designed to maintain a modest pressurisation of the tanks when the aircraft is in flight, but to allow venting when required.
Aircraft fuel tanks are now subject to fuel tank flammability requirements (FAR25.981b). One conventional approach to meeting this requirement is to provide an inerting system in which Nitrogen Enriched Air (NEA) is generated by an On Board Inert Gas Generating System (OBIGGS) which is then pumped into the fuel tanks.